A method having the described feature is known from EP 1 989 021 B1. In the camshaft described there, the shaft body forms a hollow external shaft in which an internal shaft is arranged, wherein the internal shaft can rotate with respect to the external shaft, and wherein the first component is connected in a rotationally fixed fashion to the internal shaft. A plurality of first components in the form of cams are usually connected in a rotationally fixed fashion to the internal shaft. Furthermore, second components are provided in the form of cams which are arranged on the external shaft in a rotationally and axially fixed fashion and therefore without a gap which permits a movement. By rotating the internal shaft with respect to the external shaft in a limited, predefined range it is possible to adjust the two groups of cams with respect to one another in order to permit a variable control of the valves of a motor vehicle engine. It is therefore possible, for example, to change the ratio of the inlet time to the outlet time as a function of the load and rotational speed if the inlet valves, on the one hand, and the outlet valves, on the other are activated with the different groups of cams which can be adjusted with respect to one another.
The camshaft which is described in EP 1 989 021 B1 is composed of a plurality of parts and is correspondingly also referred to as assembled camshaft. In such an assembled camshaft there is frequently the need still to process individual components after they are combined, for example in order to grind a surface to a precisely predetermined dimension. Furthermore, it may also be expedient to process the shaft body itself in a material-removing fashion and, in particular, in a cutting fashion, in order, for example, to generate a smooth surface for a sliding bearing. During such processing there is always the risk of chips or other impurities penetrating the gap, necessary for the movement, between the shaft body and the first component, which puts the functioning of this component in jeopardy. In order to reduce this risk, EP 1 989 021 B1 proposes, according to a first variant, that simple disks which are divided in two be arranged as diaphragms next to the first component in order thereby to protect the component. Although this measure is comparatively simple, the disadvantage arises that scratches and gaps may remain, as a result of which complete protection is not ensured. Furthermore, these diaphragms must also be of a suitable size in order to cover the first component to a sufficient degree. This makes the entire processing more difficult, wherein the first component cannot be processed, or at least cannot be readily processed.
According to an alternative refinement, EP 1 989 021 B1 proposes that the first component that can move with respect to the shaft body be enclosed with a capsule which completely surrounds the first component. In this context, only a small gap remains between this closed capsule and the shaft body. In order to avoid the penetration of chips or other impurities into the capsule, fluid can be applied thereto. The fluid emerging from the gap between the capsule and the shaft body effectively prevents the ingress of chips and other impurities into the capsule. As a result of the encapsulation of the moveable first component, the latter is completely covered and can accordingly no longer be processed itself either. Furthermore, the capsule must be of a considerable size so that it can accommodate the first moveable component in its interior. This can also make the processing of the other components of the camshaft more difficult.
In addition to adjustable camshafts with an internal shaft and an external shaft, camshafts are also known in which a cam pack is arranged as a first moveable component on the shaft body in a rotationally fixed but axially displaceable fashion. Such displaceability in the axial direction can be made possible, for example, by a multi-tooth profile which extends in the longitudinal direction of the shaft body, wherein the cam pack then has, as a first moveable component, a complementary hub. Such longitudinally displaceable components in the form of cam packs can also be used for adjustment. It is therefore possible, for example, to change the position of the tip of the cam and/or the pitch of the edges of the cam in the longitudinal direction. Finally, there is even the possibility of deactivating a valve by means of longitudinal displacement by virtue of a corresponding shape of the camshaft if the corresponding cylinder is also deactivated in a partial load. Corresponding refinements of assembled camshafts are known from DE 10 2009 057 633 B3, DE 10 2010 022 708 A1 and DE 10 2009 024 455 A1.